1. Field
The present disclosure relates to a damper that regenerates the energy of input vibration.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2004-237824 discloses a vehicle electromagnetic suspension apparatus that is capable of passively addressing inputs not to be controlled while actively controlling inputs to be controlled (hereinafter referred to as “target inputs”) and that is capable of not only simplifying the active control but also improving energy efficiency (paragraph [0005] and Summary).
In order to achieve the above objects, the vehicle electromagnetic suspension apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2004-237824 includes an electromagnetic actuator 4 and a motor controller 17 (Summary and FIG. 3). The electromagnetic actuator 4 is placed in parallel with a spring element 7 between the sprung and the unsprung and is driven by an electric motor 8. The motor controller 17 calculates a displacement input into the electromagnetic actuator 4 and controls the electric motor 8 so as to generate optimal damping force corresponding to the displacement input. An electrical damping element (an electrical resistor 20 or an electrical resonant circuit 21) is connected to a control circuit in the electric motor 8 in parallel with the electric motor 8 (Summary, FIG. 4, and FIG. 7). The electrical damping element passively generates the damping force through power generation damping in the electric motor 8 against the displacement input from the unsprung. The electric motor 8 generates (regenerates) power in response to rotation of a ball screw 9 in association with the displacement of a ball screw nut 10 involved in the displacement input from the unsprung (FIG. 2).
Of the electrical damping elements, the electrical resonant circuit 21 (FIG. 7) is composed of a resistor R, a coil L, and a capacitor C in which a resonant frequency is made equal to an unsprung resonant frequency (for example, 10 Hz to 20 Hz) (paragraph [0045]). With this configuration, Japanese Unexamined Patent Application Publication No. 2004-237824 indicates that both the effective active control for the target inputs within a low frequency band including a sprung resonant frequency and the effective passive control for the target inputs near the unsprung resonant frequency, which is the resonant frequency, are achieved (paragraph and FIG. 9). The active control here is current control of the electric motor 8 intended for low-frequency vibration control including orientation control (paragraph [0037]).
As described above, in Japanese Unexamined Patent Application Publication No. 2004-237824, the target inputs within the low frequency band including the sprung resonant frequency are subjected to the active control using the current control of the electric motor 8. The target inputs near the unsprung resonant frequency are subjected to the passive control using the electrical resonant circuit 21 including the resistor R, the coil L, and the capacitor C.
When the electrical resonant circuit 21 is operated in the passive control, the orientation of output current from the electric motor 8 is continuously varied. In this case, although deterioration of the capacitor C may be accelerated if a polarized capacitor is used as the capacitor C, this problem is not considered in the Japanese Unexamined Patent Application Publication No. 2004-237824.